This invention relates to an apparatus for mooring heavy structures, such as a tank floating on the sea, to a pier, quay or the like.
As shown in FIG. 1, a structure such as a tank floating in a body of water is moored to a pier 2 by mooring means 3 positioned at two locations. Due to the presence of waves and wind, the moored structure 1 is usually subjected to a great force acting in a lateral direction, toward or away from the pier, or upward or downward as indicated at x, y or z in the drawing, or in a combined direction. In view of the volume and weight of the moored structure, the mooring means are therefore subjected to a very great force.
For use with such a large structure, only a few mooring apparatus are known. An apparatus as shown in FIG. 2 appears usable. A triangular truss 4 having a base in parallel to the structure 1 to be moored is connected thereto by two bearings 5. A shaft 7 provided with a damper 6 comprising a rubber member or a superposed assembly of dish springs is supported on a pier 2 and is slidable toward or away from the structure 1 (direction y) within a limited range d. The top of the truss 4 is connected to the outer end of the shaft 7 as by a universal joint 8.
Since at least two such mooring apparatus must be used for the structure 1, a force acting on the structure 1 toward or away from the pier 2 (direction y) or upward or downward (direction z) can be deflected and absorbed by the action of the damper, bearings and universal joint, but a force acting in a lateral direction (direction x) or in a combined direction of x, y and z (e.g. oblique direction) will subject the shaft 7 of the damper 6 to a high bending force. Accordingly special expediencies must be provided for the bearings 5 and the damper to give desired strength and action. Furthermore since it is desirable to hold the structure at least ten meters away from the pier or quay with use of the mooring apparatus, the shaft 7 would be subjected to an increasing bending force with the increase in the spacing, while increasing difficulties would then be encountered in attaching the mooring apparatus to the structure.